This invention relates generally to toilets and more specifically to those toilets that can remove waste from the bowl using a reduced amount of water.
In gravity feed toilets, such as are used in most residential homes and many buildings, a storage tank is prefilled from the water supply to a predetermined level and is controlled by a float actuated valve. When the toilet is flushed, a flush valve in the tank opens, releasing water to the toilet bowl. A siphon connects the lowermost "sump" portion of the toilet bowl to a drain pipe allowing the flushing water and waste to exit the toilet bowl. See e.g. U.S. Pat. No. 4,232,410.
However, an effective flushing process requires much more than simply adding water to the toilet bowl. Without a forceful siphon action, added water simply dilutes the waste. Accordingly, an effective flushing process comprises a series of stages.
During the first "siphoning" stage, a water jet, often, at least in part, from a separate orifice in the bowl positioned near the sump, imparts its momentum to the standing water and waste in the sump. See e.g. U.S. Pat. No. 3,131,402. This causes a first slug of water and waste, sufficient in amount to block the backflow of air, to proceed into the upleg of the siphon and over its verge to establish siphon action. The downleg of the siphon, attached to the drain pipe, is designed to insure that the siphon action continues until the original standing water and waste are completely drained. Continued application of more water prevents backwash from the siphon into the bowl when the siphon is broken.
The second "cleaning" stage, sometimes overlapping with the siphoning stage, involves the scrubbing of the sides of the bowl, usually by a series of cleaning streams of water directed downward into the bowl from the bowl's rim. Both the water jet and the cleaning streams are typically supplied by the stored water in the tank.
A third "seal recovery" stage refills the bowl to establish a seal of water. This water is sometimes provided directly from the water supply, the water in the tank having been exhausted during the earlier stage(s), and comes from diverting a small percentage of the water used to refill the tank directly into the bowl. For this reason, the amount of water used during seal recovery stage can be dependent on the time the tank takes to refill, a time that is often longer than optimal.
Increased interest in water conservation has led to the development of water conserving toilets which use less water, during each flush, than standard toilets. A standard residential toilet may use three and one-half gallons per flush, compared to a water conserving toilet which may reduce this amount by about half.
The amount of water needed for the "cleaning" and "seal recovery" stages of the flushing process can to some extent be reduced by controlling the size of the tank and bowl. Reducing the amount of water used in the "siphoning" stage, however, is more difficult because a minimum amount of water is normally required to achieve sufficient momentum to ensure reliable and complete emptying of the waste and water from the bowl. Reducing the flow of water during the siphoning stage of the flushing process may cause incomplete flushing.
Some solutions have involved the use of complex and relatively expensive systems in the tank to pressurize the water. Other solutions have relied on reducing water usage by techniques that significantly reduce the cleaning capacity of the bowl. In practice, users will often flush such toilets twice to achieve the desired waste removal. Other solutions made the front of the bowl appear very shallow, which gave a user the feeling that splashing might occur. Thus, a need exists for an improved low cost water conservation toilet.